A radial roller bearing is assembled in a rotational support section for supporting a rotating shaft, while at the same time supporting large radial loads. When it is necessary for this rotational support section to support larger radial loads, a so-called full-roller radial roller bearing that is capable of increased load capacity without the use of a retainer is used.
Various kinds of assembly apparatuses and jigs have been conventionally used in order to assemble a full-roller radial roller bearing. FIG. 11 illustrates an assembly apparatus having conventional construction that is disclosed in JP H05-329721 (A). This assembly apparatus 1 has an alignment guide member 2, a guide bar 3, a pressing cylinder 4, a roller supply means 5, a shutter member 6 and a pair of chuck members 7a, 7b. 
A through hole 8 that has a funnel-shaped receiving section in the top portion is provided in the alignment guide member 2, and passes in the axial direction through the center of the alignment guide member 2. The guide bar 3 is arranged in the vertical direction (up-down direction in FIG. 11) such that the base-end section thereof is connected to the output shaft 10 of an electric motor 9, and the tip-end section thereof is gently inserted inside the through hole 8. Plural grooves 11 that are uniformly spaced in the circumferential direction are formed on the outer-circumferential surface of the tip-end section of the guide bar 3. The pressing cylinder 4 is arranged around the middle portion of the guide bar 3, and is able to displace in the axial direction relative to the guide bar 3. The roller-supply means 5 sequentially supplies a plurality of rollers R toward an annular shaped alignment space 12 that is formed between the inner-circumferential surface of the through hole 8 and the outer-circumferential surface of the guide bar 3. The shutter member 6 is provided along the bottom-end surface of the alignment guide member 2 so as to be able to move horizontally, and is able to open and close an opening on the bottom end of the through hole 8. The pair of chuck members 7a, 7b each have a concave circular arc-shaped retaining section on the surfaces that face each other, and are able to move (horizontal movement) toward or away from each other.
During operation of the assembly apparatus 1, in a state with the opening on the bottom end of the through hole 8 closed by the shutter member 6, the roller supply means 5 sequentially supplies the rollers R toward the alignment space 12 by way of the receiving section of the through hole 8. The rollers R come in contact with the outer-circumferential surface of the guide bar 3 and are rotated and guided by the rotation of the guide bar 3 so that they are aligned parallel to each other in an annular shape on the inside of the alignment space 12. After that, the annularly aligned roller group G is held by the pair of retaining sections of the chuck members 7a, 7b, and as the shutter member 6 is moved, the opening on the bottom end of the through hole 8 is exposed. Then, by causing the pressing cylinder 4 to relatively displace downward, the tip-end surface (bottom-end surface) of the pressing cylinder 4 presses the roller group G downward from the alignment space 12 on the inside of an outer ring W that is located under the alignment guide member 2.
With this assembly apparatus 1 having conventional construction, plural rollers R are aligned inside the alignment space 12, and the roller group G can be assembled all together at the same time inside the outer ring W, so it is possible to improve the work efficiency of assembling a full-roller radial roller bearing.
However, in this assembly apparatus 1, in order to align the rollers R into an annular shape, the rollers R came into metallic contact with the outer-circumferential surface of the guide bar 3, and were rotated and guided by the rotation of the guide bar 3. Therefore, there was a possibility that the rollers R could be seized or bitten between the outer-circumferential surface of the guide bar 3 and the inner-circumferential surface of the through hole 8, causing damage to the rolling surfaces of the rollers R. Particularly, grooves 11 are formed on the outer-circumferential surface of the tip-end section of the guide bar 3 in order to increase the effectiveness of rotating and guiding the rollers R, so it becomes easier for the rolling surfaces of the rollers R to become damaged. When the speed of rotation of the guide bar 3 is increased in order to shorten the work time required for aligning the rollers R, it becomes even easier to damage the roller surfaces of the rollers R, so with this assembly apparatus 1, reducing the work time for aligning the rollers R is difficult.
JP 2008-068374 (A) discloses a simplified and downsized roller-bearing assembly apparatus for aligning plural rollers in an annular shape by sequentially dropping rollers that are arranged parallel to each other in an annular alignment space that is formed between the cylindrical inner-circumferential surface of a housing and the outer-circumferential surface of a center shaft that is arranged in the horizontal direction, and then rotating and guiding the rollers by the center shaft. However, in this assembly apparatus as well, there is a similar problem in that the rollers are seized or bitten between the outer-circumferential surface of the center shaft and the inner-circumferential surface of the housing, and there is a possibility that the rolling surfaces of the rollers could be damaged.
Furthermore, with the assembly apparatus 1 having conventional construction, after the roller group G has been assembled on the inside of the outer ring W, there is a possibility that the rollers R will tilt or will drop from the inside of the outer ring W until the inner ring is assembled on the inside of the roller group G. In this regard, JP 2009-150491 (A) discloses inserting a retainer on the inside of the roller group G in a state in which the diameter of the retainer has been elastically reduced, such that the elastic force of this retainer presses the rollers R toward the outer-ring raceway that is formed around the inner-circumferential surface of the outer ring W, and holds the rollers R. However, even the case of using this retainer, in the state immediately after the roller group G has been assembled and before the retainer has been inserted, there is a possibility that the rollers R could become tilted or drop.